What is blood, everyone knows. We see it when we injure the skin, for example, if it's cut or pricked. We know that it is dense and red. But of what does the blood consist? This is not everyone knows. And yet its composition is complex and heterogeneous. It's not just a red liquid. The color is given to it not by the plasma, but by the uniform particles in it. Let's figure out what our blood is.
What does the blood consist of?
The whole volume of blood in the human body can be divided into two parts. Of course, this division is arbitrary. The first part is peripheral, that is, one that flows in the arteries, veins and capillaries, the second - the blood that is in the blood-forming organs and tissues. Naturally, it constantly circulates through the body, and therefore the separation is formal. The human blood consists of two components - the plasma and the shaped particles that are in it. These are erythrocytes, leukocytes and platelets. They differ from each other not only in structure, but also in the function performed in the body. There are more particles, some less. In addition to the form components, various antibodies and other particles are found in the human blood. Normally, blood is sterile. But with pathological processes of an infectious nature, it can detect bacteria and viruses. So, what does the blood consist of, and in what proportions are these components? This question has long been studied, and science has accurate data. In an adult, the volume of the plasma itself ranges from 50 to 60%, and the form components - from 40 to 50% of the total blood. Is it important to know? Of course, knowing the percentage of red blood cells or leukocytes in the blood, you can give an assessment of the state of human health. The ratio of the shaped particles to the total volume of blood is called the hematocrit number. Most often, it does not focus on all components, but only on erythrocytes. This indicator is determined by means of a graduated glass tube into which blood is placed and centrifuged. In this case, the heavy components drop to the bottom, and the plasma, on the contrary, rises upward. The blood, as it were, stratifies. After that, the laboratory technicians can only calculate which part is occupied by this or that component. In medicine, such analyzes have become widespread. At present, they are made on automatic hematological analyzers.
Blood plasma
Plasma is a liquid component of blood in which there are suspended cells, proteins and other compounds. On it they are delivered to organs and tissues. What does blood plasma consist of ? About 85% is water. The remaining 15% are organic and inorganic substances. Also in the blood plasma there are gases. This, of course, carbon dioxide and oxygen. Inorganic substances account for 3-4%. These anions (PO 4 3- , HCO 3- , SO 4 2- ) and cations (Mg 2+ , K + , Na + ). Organic matter (approximately 10%) is divided into nitrogen-free (cholesterol, glucose, lactate, phospholipids) and nitrogen-containing substances (amino acids, proteins, urea). Also in the blood plasma are found biologically active substances: enzymes, hormones and vitamins. They account for about 1%. From the point of view of histology, plasma is nothing more than intercellular fluid.
Erythrocytes
So, what does the human blood consist of? In addition to plasma, it contains uniform particles. Red blood cells, or erythrocytes, are perhaps the most numerous group of these components. Erythrocytes in a mature state do not have a nucleus. In form they resemble biconcave disks. The period of their life is 120 days, after which they are destroyed. This occurs in the spleen and liver. In red blood cells contains an important protein - hemoglobin. It plays a key role in the gas exchange process. In these particles, oxygen and carbon dioxide are transported . It is the protein called hemoglobin that makes the blood red.
Platelets
What does human blood consist of except plasma and red blood cells? It contains platelets. They are of great importance. These small, denuclearized cells with a diameter of only 2-4 micrometers play a decisive role in thrombosis and homeostasis. The platelets are disc-shaped. They freely circulate in the bloodstream. But their distinctive feature is the ability to respond sensitively to vascular damage. This is their main function. When injuring the walls of the blood vessel, they, when combined with each other, "repair" the damage, forming a very dense clot, which does not allow the flow of blood. Platelets are formed after the fragmentation of their larger precursors of megakaryocytes. They are in the bone marrow. A total of one megakaryocyte is formed up to 10 thousand platelets. This is a fairly large number. The life span of platelets is 9 days. Of course, they can survive and less, since they die during clogging of the damage in the blood vessel. The old platelets disintegrate in the spleen during phagocytosis and in the liver using Kupffer cells.
Leukocytes
White blood cells, or leukocytes, are agents of the body's immune system. This is the only particle of those that is part of the blood, which can leave the bloodstream and penetrate into the tissues. This ability actively contributes to the fulfillment of its main function - protection from foreign agents. Leukocytes destroy pathogenic proteins and other compounds. They participate in immune responses, producing T cells capable of recognizing viruses, foreign proteins and other substances. Lymphocytes also produce B cells that produce antibodies and macrophages that devour large pathogenic cells. It is very important to know the composition of blood when diagnosing diseases. It is the increased number of leukocytes in it that indicates the developing inflammation.
Organs of hematopoiesis
So, after analyzing the composition and function of the blood, it remains to find out where its main particles form. They have a short lifespan, so you need to constantly update them. Physiological regeneration of blood components is based on the processes of destruction of old cells and, accordingly, the formation of new cells. This occurs in the organs of hematopoiesis. The most important of these is the human bone marrow. It is located in long tubular and pelvic bones. Blood is filtered in the spleen and liver. In these organs, its immunological control is also carried out.